Photographic processes and products



April 19, 1966 PHOTOGRAPHIC PROCESSES Filed March 9.

WI W///////////////// IIIIIIIIIIII mm We'll/III]! P. J. NAGY ETAL AND PRODUCTS I IN VEN TORJ y mm ATTORNEYS United States Patent 3,246,984 PHUTOGRAPHIC PROQIIESSES AND PRQDUCTS Paul I. Nagy, Cambridge, and Howard G. Rogers, Weston, Mass, assignors to Polaroid Corporation, Cambridge, Mass, a corporation of Delaware Filed Mar. 9, 1961, Ser. No. 94,522 13 Claims. (6]. 96-29) This invention relates to photography and more particularly to products, compositions and processes for obtaining color images.

It is accordingly a primary object of this invention to provide novel products, compositions and processes use ful for obtaining color images.

Another object is to provide novel products useful for obtaining color images by diffusion transfer processes.

Still another object is to provide novel products and processes for obtaining positive and/or negative color copies of transparencies.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the processes involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products and compositions possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing wherein:

FIGURE 1 is a longitudinal, diagrammatic, fragmentary, sectional view of a novel photographic product for carrying out the novel process of this invention, the thickness of the various layers or strata being greatly exaggerated;

FIG. 2 is a longitudinal, diagrammatic, fragmentary, sectional view of another embodiment of this invention;

FIG. 3 is a longitudinal, diagrammatic, fragmentary, sectional view of still another embodiment of this invention; and

FIG. 4 is a longitudinal, diagrammatic, fragmentary, sectional view of still a further embodiment of this invention.

It is well known in the art to prepare color images by the so-called pigment printing process. In such processes, a layer of gelatin containing coloring matter such as, for example, a dye, is placed on a suitable support and then rendered sensitive to light by the addition thereto of materials such as potassium or ammonium bichromate. The gelatin layer may be sensitized by incorporating the latter agents therein, or by applying the sensitizer as a second coating on top of the layer of gelatin. The exposed areas of the gelatin layer are rendered insoluble, whereas the unexposed areas remain soluble and may subsequently be washed away with water to obtain the color image.

Diazotype processes for preparing color images are also well known in the art. The d-iazotype process involves treating a suitable carrier or base with a sensitizing composition containing a diazo compound as the lightsensitive substance. This treated carrier or base is exposed to actinic light through a pattern, thereby decomposing the diazo compound in areas of exposure. A positive reproduction of the original is obtained by coupling the undecomposed diazo compound with an azo dye coupling component. The azo dye coupling component used for development of the image may be contained in an alkaline developing solution, as in the case of the so-called wet development or one-component process; or the sensitizing composition with which the base material is treated may contain both the diazo compound and the azo coupling component, as in the dry development, or two-component process. In the dry development process, the image is formed after exposure of the sensitized material by exposure to the action of alkaline vapors such as ammonia vapors. As was indicated above, in either the dry or wet process, the formation of the color image is predicated upon decomposition of the diazo compound in areas of exposure, thereby precluding coupling with an azo coupler in the exposed areas, while coupling in the presence of an alkaline environment occurs in the unexposed areas to form an azo dye image.

Another process for preparing color images is disclosed in the copend-ing application of Howard G. Rogers, Serial No. 94,521, filed concurrently herewith. The aforementioned application is directed to the formation of color images by diffusion transfer processes employing a light-sensitive, permeable polymeric material as the light-sensitive element. In areas of exposure, the permeable polymeric material h-ardens, thereby reducing the permeability 1 in exposed areas to a solution of color image-forming constituents. In this manner, diffusion of color image-forming constituents occurs only in and/or through the areas of the light-sensitive polymeric material which are unexposed or only slightly exposed and consequently remain permeable.

The present invention is also directed to the formation of color images by the utilization of materials which are ordinarily permeable but are capable of becoming impermeable and/ or insoluble upon exposure to actinic light.

We have now discovered that light-sensitive diazo compounds-may be employed as the light-sensitive element in processes such as those described and claimed in the afore-mentioned copending application of Howard G. Rogers, Serial No. 94,521. As previously mentioned in the description of the prior art diazotype processes involving a selective coupling in unexposed or slightly exposed areas to form an azo dye, a light-sensitive diazo compound decomposes in areas exposed to actinic light. We have now found that, where exposed to actinic light, diazo compounds may act as a barrier, thus preventing the transfer of dye and/ or dye solvent in areas of exposure.

When the light-sensitive diazo compounds are selectively exposed to actinic radiation, a differential impermeabil-ity or hardening occurs proportional, areawise, to the incidence of actinic radiation. Thus, according to one embodiment of the invention, the distributive diffusion of a dye or dyes, or the color-forming components thereof, may be determined by exposure and, consequently, differential hardening of exposed areas, thereby permitting selective diffusion of color-forming constituents only through unexposed or partially exposed areas of the lightsensi-tive material.

As used herein, the expression permeable denotes the light-sensitive materials permeability to a photographic solution in the absence of exposure. Exposure results in a reduction in this permeability in the areas of exposure as a function of the point-to-point degree of exposure, and the exposed light-sensitive layer may be said to exhibit differential permeability or differential impermeability.

Since virtually all diazo compounds are sensitive to light, at least to some extent, a vast number of suitable light-sensitive diazo compounds are available for the practice of this invention. The patent literature is replete with references to the use of light-sensitive diazo compounds in photographic processes, and it is contemplated that any of the diazo compounds disclosed in the prior patent literature, for example, may be employed in the practice of the novel diffusion transfer processes of this invention.

As illustrative of such light-sensitive diazo compounds, mention may be made of the diazo resins disclosed in US. Patent No. 2,714,066. Particularly satisfactory results have been obtained with Fairmount Diazo Resin, No. 4, the trade name of a methylene-linked polymer of p-diazodiphenylamine, manufactured by the Fairmount Chemical Company, Inc. If desired, light-sensitive diazo compounds which are also dyes may be employed. In this manner, a single compound may be used both as the light-sensitive substance and as the image-forrning constituent, or, alternatively, it may be used in combination with a suitable dye in conventional manner. As illustrative of light-sensitive diazo compounds which are also dyes, mention may be made of the diazonium salts obtained from Direct Blue 1.

The invention may .best be understood by referring to the accompanying drawing.

FIGURE 1 illustrates one embodiment of the invention. A dye or number of dyes are contained in a layer adjacent to and associated with a layer 11 of a lightsensitive diazo compound in an amount sufficient to act as a barrier against diffusion of dye in areas of exposure. The dye or dyes employed may be any of the soluble dyes well known in the art. Upon exposure to actinic light, the exposed areas of the diazo compound undergo a modification quantitatively reducing the liquid permeability of the exposed areas in proportion to the amount of exposure per unit area thereof and, consequently, serve as a barrier against transfer of dye from layer 10. A suitable dye solvent may then be applied, preferably by rupturing a frangible container 12 and dispersing the solvent contained therein. Container 12 may be ruptured, for example, by passage through a pair of rollers according to procedures disclosed in the United States Patent No. 2,634,886 issued to Edwin H. Land. The dye solvent, which is capable of permeating only the unexposed areas as a result of the reduced permeability of exposed areas, acts as a carrier for the transfer, .by imbibition, of dye from layer 10 to a print-receiving layer or stratum '13 held in such close proximity to layer 11 that a substantially imagewise distribution of dye, in terms of the unexposed areas of the light-sensitive diazo layer, is transferred to the print-receiving layer 13. Following formation of the positive dye image in print-receiving layer 13, the light-sensitive diazo layer 1 1 and the print-receiving layer 13 may be separated, as by being stripped apart. Where desired, a suitable support layer '15 may be associated with the light-sensitive layer and/or the print-receiving layer to provide increased structural. strength and stability.

Another embodiment of the invention comprises a unitary layer system, as illustrated in FIG. 2, in which the dye or dyes are incorporated in a layer 14 of a light-sensitive diazo compound. As in the embodiment illustrated in FIG. 1, the permeability of the light-sensitive layer is quantitatively reduced inthe exposed areas, so that a substantially imagewise distribution of dye in terms of the unexposed areas of the light-sensitive layer 14 is transferred, by imbibition, to a print-receiving stratum 13 held in close proximity to layer 14. It should be noted that the embodiment illustrated in FIG. 2 is identical with that illustrated in FIG. 1 with but one exception. This exception is that, in the embodiment illustrated in FIG. 1, the photosensitive element contains the light-sensitive diazo compound and the color image-forming constituents in separate layers 10 and '11, whereas in the embodiment illustrated in FIG. 2, they are both in a single layer 14.

A still further embodiment of the invention is illustrated in FIG. 3, wherein a dye is incorporated in a layer 16 carried by a suitable support 15. Dye layer 16 is held in close proximity to an exposed layer of a light-sensitive diazo compound, frangible container 12 is ruptured to release a suitable dye solvent which is absorbed into dye layer 16 and into the unexposed areas of layer 11, thereby transferring a substantially imagewise distribution of the dye from dye layer 16, by imbibition, to the unexposed areas of light-sensitive layer 11, imparting thereto a positive image in terms of the unexposed areas of light-sensitive layer 11. In this manner, a negative image may also be obtained in the negative dye layer 16 in terms of the exposed areas of light-sensitive layer 11. It will be appreciated that the desired transfer will be appreciably improved if the unexposed portions of the light-sensitive diazo compound exhibit a selective affinity or mordant action toward the dye.

In the embodiment illustrated in FIG. 4, the dye or dyes may be incorporated in a dye solvent in frangible container 18 and a layer 11 of light-sensitive diazo compounds is coated onto an image-receiving sheet 13. Subsequent to exposure, frangible container 18 is ruptured and the solution of dye diffuses, by imbibition, through the unexposed areas of layer 11 to yield on and/or in print-receiving stratum 13 and in layer 11 an imagewise distribution of dye in terms of the unexposed areas of the light-sensitive diazo compound. Application of the dye solvent may be facilitated by the use of an impermeable spreading sheet 17. If desired, a suitable stripping layer may be provided between the light-sensitive layer 11 and the image-receiving layer 13, thereby facilitating separation of the two layers after formation of the dye image in or on image-receiving layer 13. v

In a modification of the procedure illustrated in FIG. 4, the light-sensitive layer maybe self-supporting or mounted on a thin, permeable support. After exposure, and either before or after application of the dye solvent between the light-sensitive layer and the spreading sheet, the image-receiving layer may be applied to the back of the light-sensitive layer to receive the dye transferring therethrough.

As was indicated previously, a color image may be obtained by diffusion transfer processes such as illustrated in FIGS. 1-4 by utilizing a light-sensitive diazo compound in combination with any of the soluble dyes well known in the art. In the embodiments heretofore described, a positive transfer image was obtained by diffusion of color image-forming components only in unexposed areas of the light-sensitive element, the exposed areas acting as a barrier to preclude transfer of the imageforming components. Also, it should be noted that if substantially all of the dye in unexposed areas is transferred, there will remain a negative image in terms of the subject matter, so that it is within the scope of the invention to obtain both a negative and a positive image.

It has been found that it is also possible, in certain situations, to obtain a negative transfer image when utilizing the diffusion transfer mechanisms illustrated in FIGS. 1 and 2.

We have discovered that when a light-sensitive diazo resin such as the Fairmount Diazo Resin previously mentioned is employed in combination with a soluble dye which is a sulfonic acid salt, it is possible to obtain either a positive or negative transfer image, depending upon the amount of diazo compound utilized in the light-sensitive element. When the concentration of diazo resin in layer 11 is relatively small, such as when layer or stratum 11 is coated with a 1% solution of diazo resin, a negative transfer image may be obtained. Where the concentration of diazo resin is raised, however, a positive transfer image is obtained.

The exact reason for this interesting behavior is not clear. However, it is believed that the sulfonate group of the dye ionizes in the coating solution and reacts with the diazo resin to form a relatively insoluble diazo sulfonate. It is believed that this relatively insoluble sulfonate is broken down again upon exposure to light, thus releasing a soluble dye in areas of exposure. Due to the differential in solubility and where the light-sensitive diazo resin is present in relatively small amounts, the color image-forming constituents transfer, by imbibition, in the areas of exposure to form a negative image on printreceiving stratum 13 in terms of the exposed areas of light-sensitive layer 11. Where the diazo resin is present in greater concentration, however, the barrier effect apparently supersedes the salt formation effect, precluding transfer of the dye in exposed areas. It may be desirable, in this connection, to add a suitable organic solvent, such as methanol, to the processing composition in order to obtain a positive transfer image of greater density, al though a positive image may be obtained without the use of such organic solvents. It should be noted that a diazo sulfonate may be formed of a diazonium compound which is not a polymer or resin, e.g., a monomeric diazonium compound. As illustrated in Example 11, infra, exposure to light decomposes the dye diazo sulfonate and the released dye is transferred to form a negative image.

In all of the examples given herein to illustrate the present invention, reference has been made to the formation of a single transfer image. It is to be understood however that, where desired, a multiplicity of prints may be formed by transferring a plurality of dye images to a plurality of successively superposed image-receiving layers. This is particularly effective in the embodiment illustrated in FIG. 4, wherein the exposed light-sensitive layer may be used in a manner similar to a stencil. The number of multiple copies formed is necessarily dependent upon exhaustion of the soluble dye capacity, which in turn is dependent upon the quantum of soluble dye and/ or solvent utilized, which in turn may be varied over a substantial range to suit the requirements of the practitioner.

In addition to the use of mpturable containers such as disclosed in the afore-mentioned Patent No. 2,634,886 and illustrated in FIGS. 1-4, application of a suitable dye solvent or dye solution to the light-sensitive element may also be accomplished, for example, by immersing, coating, spraying, flowing, etc., the light-sensitive element be ing superposed on a sheet-like image-receiving element either prior to, during or subsequent to application.

The image-receiving element, which comprises at least a dyeable material, may be selected from those which are well known and commonly used in photographic processes and may be either opaque or transparent, depending upon whether the practitioner desires a color reflection print or a color transparency. The image-receiving element may comprise a single sheet of permeable material or it may comprise a support which carries a stratum or strata of permeable image-receiving materials.

The image-receiving element may contain agents adapted to mordant or otherwise fix the transferred color imageforming constituents in order to build up a greater density of image dye. The use of a mordant in an image-receiving element is disclosed in Patent No. 2,559,643.

The light-sensitive diazo compounds may be appropriately sensitized by the addition of suitable additives. Additive agents of a character suitable for effectuating an increase in the relative speed of the light-sensitive layers reaction and/or an amplification of the effect of the incidence of actinic radiation and/ or an increase in the spectral range available to effect the excitation of the light-sensitive material are well known in the art. Thus, for example, the sensitivity of a given light-sensitive diazo compound may be extended to a greater portion, if not to all, of the visible spectrum by the incorporation in the light-sensitive layer of suitable sensitizers. Likewise, the sensitivity of a given light-sensitive diazo compound may be appropriately restricted to specific wavelengths of the spectrum by coating on or otherwise applying appropriate filter agents.

The liquid processing composition used in carrying out this invention comprises at least a liquid of sufficient solvent activity to act as a dye carrier for the diffusion of the particular dye or dyes employed. The solvent may be water or an organic solvent or a mixture of both. Suitable organic solvents, such as hydrocarbons, chlorinated hydrocarbons, alcohols, ketones and the like are well known in the art. The liquid processing composition may also contain suitable acidic or alkaline materials necessary to increase solvent activity where found expedient or desirable to incorporate such additives. In other words, where a given dye is more soluble in an acid environment, for example, it is contemplated that a suitable acid, such as a strong mineral acid, be added to the solvent. It will be apparent that the solvent, pH, etc., are also selected so as to have minimum effect on the exposed areas of the light-sensitive layer.

It should be apparent from what has been said that the rate of color-image formation is in part determined by the rate that the dye-carrier permeates the unexposed areas of the differentially hardened light-sensitive layer, and the rate of image formation may therefore be controlled in part by the selection of a solvent which exhibits the desired rate of permeation.

A viscosity-increasing compound constituting a filmforming material of the type which, when spread over a water-absorbent base, will form a relatively firm, dimensionally stable film is preferably included in the liquid processing composition in order to assist in carrying out the uniform spreading of the composition between layers of the film unit. A suitable film-forming material is a high molecular weight polymer as, for example, a polymeric, water-soluble ether, such as hydroxyethyl cellulose or sodium carboxymethyl cellulose. Filmforming compositions of this nature are described in Patent No. 2,559,643.

It is also contemplated that, where desired, an auxiliary hardening agent, or agents, which do not adversely affect the dye or dyes, may be added to the processing composition to effect an increase in the hardness and therefore a decrease in the permeability of the exposed light-sensitive material. Hardening agents of this nature are well known in the art.

To provide image-forming constituents, a large number of dyes, capable of being solubilized and diffused through a permeable light-sensitive material, are available for the practice of this invention. Among the large number of complete dyes, mention may be made of monoazo, diazo and anthraquinone dyes. The field of dye materials may be further extended by the employment of dye substances of the type which are colorless or of a color other than that ultimately desired in a particular environment, for example, in an acid environment, but upon change in the environment, such as a change in pH, take on a color change. Dye substances of this type include indicator dyes, leuco dyes and carbinols of basic dyes.

In addition to the afore-mentioned classes of dyes useful in the practice of this invention, all of which are well known in the art, particular mention may be made of those dyes which are capable of a salt formation upon contact with the diazo compound, as heretofore mentioned. Among the dyes capable of forming a diazo sulfonate upon contact with a light-sensitive diazo compound, mention may be made of the following:

C.I. Acid Blue 18 01. Acid Blue 34 SO3N3.

H l 2 SO Na C.I. Acid Green 5 The range of image-forming constituents useful in the practice of this invention may further be extended by the use of materials which will combine, at some time subse quent to exposure, to form the desired color image. For example, it is within the scope of this invention to transfer, by imbibition, a color coupler which will couple With an oxidized color developer contained in or on the imagereceiving layer. The diffusion-transfer processes of this invention may also be utilized to control the transfer of color-forming components which will effect a color change in a predyed image-receiving layer, for example, to control the transfer of a reducing agent in a color system wherein an oxidized monomeric or polymeric indolphenol dye is disposed in or on a suitable image-receiving element. Thus, in such a system, a selective reduction of the oxidized indolphenol dye or dyes may be effected to provide loss of color in or on the image-receiving element in terms of the unexposed areas of a selectively exposed light-sensitive differentially permeable element.

The following examples are given to show by way of illustration and not by way of limitation the novel photographic products, compositions and processes of this invention.

EXAMPLE 1 A subcoated cellulose acetate sheet was coated with a layer of 4% gelatin solution containing 3% Acid Blue 18 and the coating was allowed to dry. Thereafter, a second coating of an 0.8% aqueous solution of Fairmount Diazo Resin No. 4 was applied on top of the first coating. The coated sheet was then exposed for 1 minute. After exposure, it was imbibed for 3 minutes with an aqueous solution containing 3% hydroxyethyl cellulose, whereby a negative transfer image was obtained.

EXAMPLE 2 The experiment illustrated in Example 1 was repeated, using exposures of 5, and minutes. In each case, a negative transfer image was obtained.

' EXAMPLE 3 The above experiments were repeated, substituting Acid Green 5 or Acid Blue 34 for the Acid Blue 18. In each case, a negative transfer image was obtained.

EXAMPLE 4 A 4% gelatin solution containing 4% Acid Blue 18 was coated onto a subcoated cellulose acetate sheet and then dried. Thereafter, a second coating of a 10% aqueous solution of Fairmount Diazo Resin No. 4 was applied. The coated sheet was exposed for 3 minutes and then imbibed for 2 minutes with an aqueous solution containing 3% hydroxyethyl cellulose, thereby forming a positive transfer image.

EXAMPLE 5 The above experiment was repeated, except that the imbibition was with a processing solution comprising 1 part by weight of methanol to 3 parts of the aqueous solution containing 3% hydroxyethyl cellulose. A denser transfer image was obtained.

EXAMPLE 6 A subcoated cellulose acetate sheet was coated with a 4% gelatin solution containing 4% Acid Blue 34. After drying, a second coating of a 7% aqueous solution of Fairmount Diazo Resin No. 4 was applied. Exposure and imbibition was substantially the same as in Example 4 and a positive transfer image was likewise obtained.

EXAMPLE 7 Two unitary layer light-sensitive elements were prepared by coating 21 subcoated cellulose acetate sheet with a 0.5% gelatin solution containing 4% Acid Blue 34 and 5% Fairmount Diazo Resin No. 4. One light-sensitive element prepared in this manner was exposed for 5 minutes, and the second one was exposed for 20 minutes. Both were imbibed for 1 minute with an aqueous solution containing 3% hydroxyethyl cellulose. In both instances, a positive transfer image was obtained.

EXAMPLE 8 In the above examples, the di-azo resin showed sensitivity substantially only to blue light. In this example, the procedure set forth in Example 7 was repeated, adding trace amounts of a mixture of thiourea and Basic Green 1 to the dye and diazo resin coating solution. A positive transfer image was obtained showing sensitivity to be extended into the red.

EXAMPLE 9 A light-sensitive element was prepared by coating baryta paper with an aqueous solution containing diazotized Direct Blue 1. It was then exposed for 2 minutes and imbibed for 3 minutes with a processing solution comprising 1 part by weight of tetrahydrofuran to 3 parts of an aqueous solution of 4% carboxymethyl cellulose. A negative transfer image was obtained.

EXAMPLE 10 Following imbibition as illustrated in Example 9, the light-sensitive element was uniformly re-exposed for 2 minutes and then subjected to a second imbibition period. A positive transfer image was formed.

It should be noted that in the procedures illustrated in Examples 9 and 10, both a positive and a negative transfer image were obtained from a single latent image formed as a result of the initial exposure of the light-sensitive element.

EXAMPLE 11 A layer of 4% gelatin containing 4% Acid Blue 34 was coated onto a subcoated cellulose sheet. After drying, a second coating of a 0.5% gelatin solution containing 7% Fast Blue BB Salt was applied. The coated negative sheet was exposed for minutes and then imbibed for 1 minute with an aqueous solution containing 3 hydroxyethyl cellulose, to obtain a positive transfer image.

In most of the above examples, a small amount of gelatin was added to the coating solution in order to facilitate application of the coating in a uniform manner. It is expressly to be understood that the use of the gelatin, or equivalent materials, is not necessary to the practice of this invention, the gelatin being used only as a matter of convenience. It is further to be understood that the invention is not limited'to the proportions given or the materials employed, and the foregoing examples are given only to illustrate the practice of this invention.

The invention as described in the specification and defined in the appended claims is particularly useful in preparing color copies of positive or negative transparencies, although it will be apparent that the invention is not limited thereto.

The expression color as used throughout the specification and claims is intended to include the use of a plurality of colors to obtain black, as Well as the use of a single black dye.

Since certain changes may be made in the above prod ucts, compositions and processes without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. The process of forming positive color images which comprises exposing a light-sensitive element comprising a light-sensitive diazo compound and a soluble sulfonate salt of a dye, said diazo compound in said light-sensitive element being present in an amount suflicient to form a barrier for said dye in exposed areas, thereby precluding diffusion of said dye through said exposed areas of said diazo compound; contacting said exposed light-sensitive element with a processing composition comprising at least a solvent for said dye, said solvent being present in an amount sufficient to form an imagewise solution of said dye in terms or" unexposed and partially exposed areas of said diazo compound; and diffusing said imagewise dye solution, at least in part, through unexposed and partially exposed areas of said diazo compound to a superposed image-receiving element to form thereon a positive image comprising essentially said dye.

2. The process of claim 1 wherein said light-sensitive diazo compound is a methylene-linked polymer of p-diazodiphenylamine.

3. The process of claim 1 wherein said dye is selected from the group consisting of Acid Blue 34, Acid Blue 18 and Acid Green 5.

4. The process of forming negative color images vwhich comprises exposing a light-sensitive element containing the reaction product of a light-sensitive diazo compound and a soluble sulfonate salt of a dye to release said dye in areas of exposure, said released dye being more soluble than said reaction product, the concentration of said diazo compound in said light-sensitive element being relatively small so as not to preclude diffusion of said dye in exposed areas; contacting said exposed light-sensitive element with a processing composition comprising at least a solvent for said dye; and selectively transferring, by imbibition, an imagewise distribution of said dye in terms of exposed and partially exposed areas of said light-sensitive element to a superposed image-receiving element, thereby forming a negative transfer dye image.

5. The process of claim 4 wherein said light-sensitive diazo compound is a methylene-linked polymer of p-diazodiphenylamine.

'6. The process of claim 4 wherein said dye is selected from the group consisting of Acid Blue 34, Acid Blue 18 and Acid Green 5.

7. The process of forming images in color which comprises exposing a light-sensitive element comprising a light-sensitive diazo compound and at least one dye, thereby quantitatively reducing the liquid permeability of the exposed areas of said light-sensitive diazo compound in proportion to the amount of exposure per unit area thereof, whereby said exposed areas of reduced permeability serve as a barrier against diffusion of said dye from said light-sensitive element when said element is contacted at some. time subsequent to exposure with a processing composition; thereafter contacting said exposed element with said processing composition comprising essentially a solvent for said dye, said solvent being present in an amount sufficient to form an imagewise solution of said dye in terms of unexposed and partially exposed areas of said diazo compound; and diffusing said imagewise solution, at least in part, through said unexposed and partially exposed areas of said diazo compound to a superposed image-receiving layer to form thereon a positive image comprising essentially only said dye.

'8. The process of forming color images which comprises exposing a light-sensitive element comprising a light-sensitive diazo compound, thereby quantitatively reducing the liquid permeability of the exposed areas of said light-sensitive diazo compound in proportion to the amount of exposure per unit area thereof, whereby said exposed areas of reduced permeability serve as a barrier against diffusion therethrough of a solution containing at least one dye; and thereafter contacting said exposed element with said dye-containing solution, said dye being present initially exterior to said light-sensitive element, whereby said dye-containing solution dififuses through said unexposed and permeable areas of said diazo compound to form a positive dye image therebeneath.

9. The process of forming images in col-or which com prises exposing a light-sensitive element comprising a light-sensitive diazo compound, said diazo compound being the diazotization product of a diazotizable sulfonated dye; contacting said exposed element with a processing composition comprising at least a solvent for said compound; and selectively transferring, by imbibition, an imagewise distribution of said compound in terms of exposed and partially exposed areas to a superposed imagereceiving element, thereby forming a negative color image on said image-receiving element.

10. The process of forming images in color which comprises exposing a light-sensitive element comprising diazotized Direct Blue 1; contacting said exposed light-sensitive element with a processing composition comprising at least a solvent for said compound; and selectively transferring, by imbibition, an imagewise distribution of said compound in terms of exposed and partially exposed areas to a superposed image-receiving element, thereby forming a negative color image.

11. A process as defined in claim 10 including the steps of re-exposing said light-sensitive element at some time subsequent to said contacting step; re-contacting said reexposed light-sensitive element with a second processing composition comprising at least a solvent for the said compound remaining in said re-exposed light-sensitive element; and transferring, by imbibition, at least a portion of the remaining said compound in said light-sensitive element to a second superposed image-receiving element, thereby forming a positive color image on said second image-receiving element.

'12. A photographic product comprising a support, a light-sensitive diazo compound in a layer on said support, and a dye in a layer on the same side of said support as said diazo compound, said dye being selected from the group consisting of Acid Blue 34, Acid Blue 18, and Acid Green 5.

13. The product as defined in claim 12, further including a frangible container having therein a processing solution comprising at least a solvent for said dye.

(References on following page) 1 1 References Cited by the Examiner 3,010, 391 UNITED STATES PATENTS 3,030,207

12/1879 Edwards 101149.4

2/1922 Thornton 101--149. 1

' 11/1 937 Zahn 96-91 5 2/ 1953 Land 9675 X 80497 9/1953 Land 96-429 J 1 7/1955 Jewett et a1. 96-33 X 3/1958 Hodgins 96-91 9/1961 vForis 96-29 12 11/1961 Buskes et' a1. 101-1492 4/ 196 2 Land 9629 FOREIGN PATENTS 4/ 1956 Australia. 10/1934 Great Britain. 11/1958 Great Britain.

NORMAN G. TORCHIN, Primary Examiner. PHILIP E. MANGAN, Examiner. 

1. THE PROCESS OF FORMING POSITIVE COLOR IMAGES WHICH COMPRISES EXPOSING A LIGHT-SENSITIVE ELEMENT COMPRISING A LIGHT-SENSITIVE DIAZO COMPOUND AND A SOLUBLE SULFONATE SALT OF A DYE, SAID DIAZO COMPOUND IN SAID LIGHT-SENSITIVE ELEMENT BEING PRESENT IN AMOUNT SUFFICIENT TO FORM A BARRIER FOR SAID DYE INEXPOSED AREAS, THEREBY PRECLUDING DIFFUSION OF SAID DYE THROUGH SAID EXPOSED AREAS OF SAID DIAZO COMPOUND; CONTACTING SAID EXPOSED LIGHT-SENSITIVE ELEMENT WITH A PROCESSING COMPOSITION COMPRISING AT LEAST A SOLVENT FOR SAID DYE, SAID SOLVENT BEING PRESENT IN AN AMOUNT SUFFICIENT TO FORM AN IMAGEWISE SOLUTION OF SAID DYE IN TERMS OF UNEXPOSED AND PARTIALLY EXPOSED AREAS OF SAID DIAZO COMPOUND; AND DIFFUSING SAID IMAGEWISE DYE SOLUTION, AT LEAST IN PART, THROUGH UNEXPOSED AND PARTIALLY EXPOSED AREAS OF SAID DIAZO COMPOUND TO A SUPERPOSED IMAGE-RECEIVING ELEMENT TO FORM THEREON A POSITIVE IMAGE COMPRISING ESSENTIALLY SAID DYE. 